JP2014010331A - Imaging lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an imaging lens of a wide angle of view, in which F number is small and both a smaller size and higher definition are achieved.SOLUTION: An imaging lens, composed of five lenses for solid imaging element, comprises in order from an object side to the image side: an aperture diaphragm; a first lens of positive refractive power, the convex face of which is oriented toward the object side; a second lens of negative refractive power, the concave face of which is oriented toward the image side; a third lens of positive refractive power, the convex face of which is oriented toward the image side; a fourth lens of negative refractive power, both faces of which are aspheric and the concave face of which is oriented toward the object side near an optical axis; and a fifth lens of negative refractive power, with a meniscus shape, both faces of which are aspheric, and the concave face of which is oriented toward the image side near the optical axis. The fifth lens has a shape that decreases the negative refractive power as it is located farther from the optical axis. The imaging lens satisfies the following conditional formula (1): 0.55<f1/f<1.0 in which f is the focal distance of the entire imaging lens and f1 is the focal distance of the first lens.

Description

  The present invention provides an imaging device mounted on an imaging device using a solid-state imaging device such as a relatively small and thin CCD sensor or a CMOS sensor mounted on a portable terminal such as a mobile phone or a smartphone, a PDA (Personal Digital Assistance), or the like. It relates to lenses.

  2. Description of the Related Art In recent years, a camera function is now naturally added to portable terminals such as mobile phones and smartphones, and devices such as PDAs. In addition, in order to improve portability and convenience, these devices are being studied for further miniaturization and thinning, and at the same time, improvement of camera functions corresponding to higher pixels is also being considered. For this reason, image sensors used in image pickup apparatuses mounted on these devices are in a situation where the size and the number of pixels are increasing. In addition, an imaging lens mounted on an imaging device is required not only to have a high resolving power corresponding to an increase in the number of pixels but also to be adapted to a reduction in size and thickness. In addition, there is an increasing demand for a bright lens system for adapting to high-density imaging devices and a wide angle of view capable of capturing a subject image in a wide range.

  Conventionally, as an imaging lens mounted on the above-described device, an aberration of some degree can be corrected, and an imaging lens having a three-lens configuration which is advantageous in terms of size and cost has been widely used. Accordingly, many imaging lenses having a four-lens configuration that can be expected to have higher performance than the three-lens configuration have been proposed. However, in recent years, the increase in the number of pixels in image pickup devices has further evolved, and devices equipped with camera functions far exceeding 5 megapixels have also appeared. In order to cope with such a trend of increasing the number of pixels, an imaging lens having a five-lens configuration capable of achieving higher resolution and higher performance than the four-lens configuration has been proposed.

  For example, in Patent Document 1, in order from the object side, a positive first lens having a convex surface on the object side, a second meniscus second lens having a concave surface on the image surface side, and a convex surface on the image surface side are disclosed. A positive meniscus third lens directed to the opposite side, a negative fourth lens having aspherical surfaces on both sides and a concave surface near the optical axis, and a positive or negative fifth lens having aspherical surfaces on both sides An imaging lens having the above is disclosed.

  Patent Document 2 discloses a first lens group including a first lens convex from the object side to the object side, a second lens group including a concave second lens on the imaging side, and a concave meniscus on the object side. A third lens group including a third lens having a shape, a fourth lens group including a fourth lens having a concave meniscus shape on the object side, and a fifth meniscus shape having an aspheric surface having an inflection point on the object side. An imaging lens system including a fifth lens group including a lens is disclosed.

JP 2007-264180 A JP 2011-085733 A

  The imaging lens described in Patent Document 1 has a five-lens configuration and optimizes the lens material and the surface shape of the lens, thereby obtaining a correction effect for axial chromatic aberration and lateral chromatic aberration, and high performance corresponding to an increase in the number of pixels. The imaging lens system is realized. However, the total optical length is about 8 mm, and there remains a problem in application to devices that are becoming thinner. Further, the F value is about 2.8 and the angle of view is about 32 °, and it cannot sufficiently cope with a bright lens system and a wide angle of view that have recently been required.

  In addition, the imaging lens described in Patent Document 2 has a high optical resolution and an optical total length of about 6 mm, and is relatively small and thin. However, the F value is about 2.8 and the angle of view is about 32 °, and the specifications (high resolution, small size, thin, bright lens system, wide angle of view) that have recently been required for the imaging lens described in this document. Can not be satisfied enough.

The present invention has been made in view of the above-described problems. The object of the present invention is to reduce the size and thickness of the five-lens configuration, and to achieve a high resolution while having a small F value and a wide image. An object of the present invention is to provide an imaging lens that can handle corners.
Note that the terms “miniaturization” and “thinning” as used herein mean that the maximum image height of an image formed by the imaging lens is IH, and the distance on the optical axis from the most object side surface constituting the imaging lens to the imaging surface is the optical total length. When TTL is used, it indicates a level that is miniaturized to the extent that TTL / (2IH) <1.0 is satisfied. For example, this indicates a level where the optical total length of the imaging lens is shorter than the diagonal length of the effective imaging surface of the imaging device.
The F value has a brightness of about F2.6 or less, and the field angle indicates a wide field angle level of 70 ° or more over the entire field angle.

An imaging lens according to the present invention is an imaging lens composed of five lenses for a solid-state imaging device, and has a positive refractive power with an aperture stop and a convex surface facing the object side in order from the object side to the image side. A first lens having a negative refractive power with a concave surface facing the image side, a third lens having a positive refractive power with a convex surface facing the image side, both surfaces formed of aspherical surfaces, and an optical axis A fourth lens having negative refractive power with a concave surface facing the object side in the vicinity, and a fifth lens having negative meniscus shape with both surfaces formed of aspheric surfaces and having a concave surface facing the image side near the optical axis The fifth lens has a shape in which the negative refractive power decreases as the distance from the optical axis increases. Further, in this configuration, the following conditional expression (1) is satisfied.
(1) 0.55 <f1 / f <1.0
Here, f is the focal length of the entire imaging lens system, and f1 is the focal length of the first lens.

  The imaging lens having the above-described configuration includes, among the five lenses, when the first lens, the second lens, and the third lens are the front group, and the fourth lens and the fifth lens are the rear group, the front group is The rear group has a structure close to a so-called telephoto type having a positive refractive power as a whole and a negative refractive power as a whole. By adopting such a configuration and making the image side surface of the fifth lens concave, it is easy to shorten the optical total length. In addition, by forming appropriate aspheric shapes on both surfaces of the fourth lens and the fifth lens, various aberration correction effects and an effect of suppressing the angle of light rays incident on the image sensor are obtained.

  Conditional expression (1) regulates the ratio of the focal length of the first lens and the focal length of the entire imaging lens to an appropriate range, and suppresses shortening of the total optical length and occurrence of off-axis aberrations. This is a condition for enabling good aberration correction. If the upper limit of conditional expression (1) is exceeded, the positive power of the first lens occupying the power of the entire imaging lens system becomes too weak, which is advantageous in reducing the manufacturing error sensitivity of the lens. It is disadvantageous for shortening, and it is difficult to realize miniaturization and thinning. On the other hand, if the lower limit value of conditional expression (1) is not reached, the positive power of the first lens occupying the power of the entire imaging lens system becomes too strong, and it is particularly difficult to correct astigmatism and curvature of field. In addition, the manufacturing error sensitivity of the lens is increased, and the assembly accuracy is deteriorated.

Moreover, it is desirable that the imaging lens of the present invention satisfies the following conditional expressions (2) to (6).
(2) 50 <ν1 <70
(3) ν2 <35
(4) 50 <ν3 <70
(5) 50 <ν4 <70
(6) 50 <ν5 <70
Where ν1 is the Abbe number of the first lens, ν2 is the Abbe number of the second lens, ν3 is the Abbe number of the third lens, ν4 is the Abbe number of the fourth lens, and ν5 is the Abbe number of the fifth lens.

  Conditional expressions (2) to (6) define the Abbe number range of each lens material, and are conditions for satisfactorily correcting axial chromatic aberration and lateral chromatic aberration. According to conditional expressions (2) to (6), the second lens is formed of a high dispersion material, and the first lens, the third lens, the fourth lens, and the fifth lens are formed of a low dispersion material. The By setting the Abbe number of four of the five lenses to a value greater than 50, axial chromatic aberration and lateral chromatic aberration can be corrected more favorably. If a material with an Abbe number exceeding 70 is used, the lens material becomes expensive, which is disadvantageous for cost reduction.

  By the way, as a method for correcting chromatic aberration, a method of combining a high dispersion material and a low dispersion material is generally known. In the case of a five-lens imaging lens, chromatic aberration can be obtained by alternately combining a lens having a positive power formed of a low dispersion material and a lens having a negative power formed of a high dispersion material. Can be corrected. However, when such a correction method is employed, there is a limit to the correction of chromatic aberration when further thinning is attempted. In other words, in a lens configuration that corrects chromatic aberration by alternately combining a high-dispersion material and a low-dispersion material, when the overall optical length is shortened, mainly in off-axis rays, The chromatic aberration of magnification often changes from an undercorrected state (short wavelength increases in the negative direction to the reference wavelength) to an overcorrected state (short wavelength increases in the positive direction with respect to the reference wavelength) toward the image height. This is because it is difficult to satisfactorily correct lateral chromatic aberration over the entire imaging surface. By satisfying conditional expressions (2) to (6) as in the present invention, the problem of undercorrection and overcorrection of lateral chromatic aberration can be avoided, and both thinning and good correction of lateral chromatic aberration can be achieved. Can do.

Moreover, it is desirable that the imaging lens of the present invention satisfies the following conditional expression (7).
(7) -1.6 <f2 / f <-0.7
Here, f2 is the focal length of the second lens.

  Conditional expression (7) defines the ratio of the focal length of the second lens to the focal length of the entire imaging lens system within an appropriate range, and suppresses the occurrence of various aberrations on and off the axis, This is a condition for shortening the overall length. If the upper limit of conditional expression (7) is exceeded, the negative power of the second lens occupying the power of the entire imaging lens system becomes too strong, and the on-axis and off-axis chromatic aberration is overcorrected (with respect to the chromatic aberration of the reference wavelength). Short wavelength chromatic aberration increases in the positive direction). In addition, the imaging surface is curved toward the image side, making it difficult to obtain good imaging performance. Furthermore, since the radius of curvature of the image-side surface of the second lens becomes too small, the possibility that stray light is generated due to total reflection of off-axis light rays is increased, which is likely to cause ghost and flare. On the other hand, if the lower limit value of conditional expression (7) is not reached, the negative power of the second lens occupying the power of the entire imaging lens system becomes too weak, which is advantageous for shortening the optical total length. In addition, off-axis chromatic aberration is undercorrected (short wavelength chromatic aberration increases in the negative direction with respect to chromatic aberration at the reference wavelength). In addition, the imaging surface is curved toward the object side, and in this case, it is difficult to obtain good imaging performance.

Moreover, it is desirable that the imaging lens of the present invention satisfies the following conditional expression (8).
(8) 1.05 <f12 / f <1.60
Here, f12 is a combined focal length of the first lens and the second lens.

  Conditional expression (8) defines the ratio between the combined focal length of the first lens and the second lens and the focal length of the entire imaging lens system within an appropriate range, and shortens the optical total length and widens the angle of view. This is a condition for enabling securing of back focus and good aberration correction. If the upper limit value of conditional expression (8) is exceeded, the positive combined power of the first lens and the second lens occupying the power of the entire imaging lens system becomes too weak, so that the focal length becomes long and the optical total length is shortened. A wide angle of view becomes difficult. On the other hand, if the lower limit value of the conditional expression (8) is not reached, the positive combined power of the first lens and the second lens occupying the power of the entire imaging lens system becomes too strong, so the focal length is shortened and the angle of view is increased. However, it is difficult to secure the back focus. If the negative power of the fourth lens and the fifth lens is increased in order to ensure the back focus, astigmatism mainly occurs off-axis, making it difficult to obtain good imaging performance. It becomes. In addition, if the radius of curvature of the lens is made small in order to obtain a large power, the manufacturing error sensitivity becomes high, which is not preferable. By defining the positive combined power of the first lens and the second lens within the range of conditional expression (8), these problems can be avoided.

  In the imaging lens of the present invention, the object side surface of the fourth lens has an aspherical shape in which the negative power is weakened toward the periphery, and the image side surface is a non-spherical shape in which the positive power is weakened toward the periphery. A spherical shape is desirable. By making the shape of the fourth lens away from the aperture stop into such an aspherical shape, the optical path length of the light beam when passing through the fourth lens can be adjusted. As a result, it is possible to satisfactorily correct various aberrations at each image height, mainly astigmatism.

In the imaging lens of the present invention, it is preferable that the following conditional expression (9) is satisfied.
(9) 1.7 <ν1 / ν2 <2.7
Here, ν1 is the Abbe number of the first lens, and ν2 is the Abbe number of the second lens.

  Conditional expression (9) is a condition for further suppressing the lateral chromatic aberration and the axial chromatic aberration.

In the imaging lens of the present invention, it is preferable that the following conditional expression (10) is satisfied.
(10) −0.80 <f1 / f2 <−0.45
f1: Focal length of the first lens f2: Focal length of the second lens

  Conditional expression (10) defines the ratio between the focal length of the first lens and the focal length of the second lens within an appropriate range, and reduces chromatic aberration and spherical surface while reducing the size and wide angle of the imaging lens. This is a condition for suppressing the aberration and the coma aberration within a favorable range. If the upper limit value of conditional expression (10) is exceeded, the negative power of the second lens becomes relatively weaker than the positive power of the first lens, which is advantageous for downsizing the imaging lens. The upper chromatic aberration and off-axis lateral chromatic aberration are undercorrected (short wavelength increases in the minus direction with respect to the reference wavelength), and in this case, it is difficult to obtain good imaging performance. On the other hand, if the lower limit value of conditional expression (10) is not reached, the negative power of the second lens becomes relatively stronger than the positive power of the first lens, and the off-axis lateral chromatic aberration is overcorrected (to the reference wavelength). On the other hand, the short wavelength increases in the positive direction). Also, coma increases for off-axis light flux. For this reason, it is difficult to obtain good imaging performance. If these aberrations are corrected by a lens arranged after the second lens, the total optical length becomes long, and it is difficult to reduce the size.

  According to the present invention, it is possible to obtain an imaging lens that can be reduced in size and thickness, achieves high resolution, has a small F-number, and can handle a wide angle of view.

FIG. 3 is a diagram illustrating a schematic configuration of an imaging lens of Example 1. FIG. 3 is a diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens of Example 1. 6 is a diagram illustrating a schematic configuration of an imaging lens of Example 2. FIG. 6 is a diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens of Example 2. FIG. 6 is a diagram illustrating a schematic configuration of an imaging lens of Example 3. FIG. 6 is a diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens of Example 3. FIG. 6 is a diagram illustrating a schematic configuration of an imaging lens of Example 4. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion of the imaging lens of Example 4. FIG. 6 is a diagram illustrating a schematic configuration of an imaging lens of Example 5. FIG. 6 is a diagram illustrating spherical aberration, astigmatism, and distortion of the imaging lens of Example 5. FIG. 6 is a diagram illustrating a schematic configuration of an imaging lens of Example 6. It is a figure which shows the spherical aberration, astigmatism, and distortion of the imaging lens of Example 6.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
1, 3, 5, 7, 9, and 11 are schematic configuration diagrams of imaging lenses according to Examples 1 to 6 of the present embodiment, respectively. Since both have the same basic lens configuration, the imaging lens configuration of the present embodiment will be described with reference to the schematic configuration diagram of Example 1.

  As shown in FIG. 1, the imaging lens of the present embodiment includes, in order from the object side to the image plane side, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, The lens includes a third lens L3 having a positive refractive power, a fourth lens L4 having a negative refractive power, and a fifth lens L5 having a negative refractive power. The aperture stop ST is disposed on the object side of the first lens L1. A filter IR is disposed between the fifth lens L5 and the image plane IM. The filter IR can be omitted. Moreover, when calculating the optical total length of an imaging lens, the value when a filter is removed shall be employ | adopted.

In the five-lens imaging lens, the first lens L1 is a biconvex lens in which both the object-side surface r1 and the image-side surface r2 are formed as convex surfaces, and the second lens L2 is the object-side surface r3. Is a meniscus lens having a convex surface and an image side surface r4 being a concave surface, and the third lens L3 is a meniscus lens having an object side surface r5 having a concave surface and an image side surface r6 having a convex surface. The fourth lens L4 is a meniscus lens in which the object-side surface r7 is concave and the image-side surface r8 is convex near the optical axis X, and the fifth lens L5 is an object-side surface r9 near the optical axis X. A convex meniscus lens having a concave surface r10 on the image side.
The object side surface r3 of the second lens L2 is a lens surface having a weak refractive power with respect to the focal length of the second lens L2, and has a relatively large radius of curvature. The shape of the object-side surface r3 of the second lens L2 is not limited to a convex surface, and may be a concave surface. The second lens L2 in Example 3 of the present embodiment is an example of a biconcave lens in which the object-side surface r3 and the image-side surface r4 are both concave.

  In the above configuration, of the five lenses L1 to L5, the first lens L1, the second lens L2, and the third lens L3 are the front group, and the fourth lens L4 and the fifth lens L5 are the rear group. In this case, the front group has a positive refractive power as a whole, and the rear group has a negative refractive power as a whole, which is a structure close to a so-called telephoto type. By making the surface concave, the overall optical length is shortened. In addition, by forming appropriate aspheric shapes on both surfaces of the fourth lens L4 and the fifth lens L5, it is possible to obtain various effects of correcting aberrations and suppressing the angle of light rays incident on the image sensor.

In addition, all the imaging lenses of the present embodiment employ a plastic material. In all the embodiments, an olefin plastic material is used for the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5, and a polycarbonate plastic material is used for the second lens L2.
By adopting plastic materials for all lenses, stable mass production is possible and cost reduction is easy. Further, the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5 are made of the same material, so that they are easy to manufacture.

The imaging lens of the present invention satisfies the following conditional expression.
(1) 0.55 <f1 / f <1.0
(2) 50 <ν1 <70
(3) ν2 <35
(4) 50 <ν3 <70
(5) 50 <ν4 <70
(6) 50 <ν5 <70
(7) -1.6 <f2 / f <-0.7
(8) 1.05 <f12 / f <1.60
(9) 1.7 <ν1 / ν2 <2.7
(10) −0.80 <f1 / f2 <−0.45
However,
f: focal length of the entire imaging lens f1: focal length of the first lens f2: focal length of the second lens f12: combined focal length of the first lens and the second lens ν1: Abbe number of the first lens ν2: second Abbe number of lens ν3: Abbe number of third lens ν4: Abbe number of fourth lens ν5: Abbe number of fifth lens

  In the present embodiment, all lens surfaces are aspherical. The aspherical shape adopted for these lens surfaces is Z in the optical axis direction, H in the direction perpendicular to the optical axis, k in the conical coefficient, A4, A6, A8, A10, A12, When A14 and A16 are set, they are expressed by the following formula.

  Next, examples of the imaging lens according to the present embodiment will be described. In each embodiment, f represents the focal length of the entire imaging lens system, Fno represents the F number, ω represents the half field angle, and IH represents the maximum image height. Further, i is a surface number counted from the object side, r is a radius of curvature, d is a distance (surface interval) between lens surfaces on the optical axis, Nd is a refractive index with respect to d-line (reference wavelength), and νd is with respect to d-line. The Abbe numbers are shown. As for the aspherical surface, a surface number i is added after the symbol * (asterisk).

The basic lens data is shown in Table 1 below.

  The imaging lens of Example 1 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 1. These aberration diagrams show the amount of aberration with respect to each wavelength of the F-line (486 nm), d-line (588 nm), and C-line (656 nm). The astigmatism diagrams show the aberration amounts on the sagittal image surface S and the tangential image surface T (the same applies to FIGS. 4, 6, 8, 10, and 12). As shown in FIG. 2, it can be seen that each aberration is well corrected.

  Further, the total optical length TTL is as short as 4.56 mm, and the ratio (TTL / 2IH) with respect to the maximum image height IH is 0.82, and downsizing is realized despite the five-lens configuration. Further, the F value is as bright as 2.52, and the half angle of view is about 35.8 °, realizing a wide angle of view.

The basic lens data is shown in Table 2 below.

  The imaging lens of Example 2 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 2. As shown in FIG. 4, it can be seen that each aberration is well corrected.

  Further, the total optical length TTL is as short as 4.48 mm, and the ratio (TTL / 2IH) with respect to the maximum image height IH is 0.80. Further, the F value is bright as 2.38, the half angle of view is about 36.0 °, and a wide angle of view is realized.

実施例３の撮像レンズは、表７に示すように条件式（１）〜（１０）の全てを満たしている。 Basic lens data is shown in Table 3 below.

The imaging lens of Example 3 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 3. As shown in FIG. 6, it can be seen that each aberration is corrected satisfactorily.

  Further, the total optical length TTL is as short as 4.65 mm, and the ratio (TTL / 2IH) with respect to the maximum image height IH is 0.83. Further, the F value is as bright as 2.58, and the half angle of view is about 35.3 °, so that a relatively wide angle of view is realized.

Basic lens data is shown in Table 4 below.

  The imaging lens of Example 4 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 4. As shown in FIG. 8, it can be seen that each aberration is corrected satisfactorily.

  Further, the total optical length TTL is as short as 4.59 mm, the ratio (TTL / 2IH) to the maximum image height IH is 0.82, and miniaturization is realized even though the configuration is five sheets. Further, the F value is bright as 2.34, the half angle of view is about 35.6 °, and a wide angle of view is realized.

Basic lens data is shown in Table 5 below.

  The imaging lens of Example 5 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 10 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 5. As shown in FIG. 10, it can be seen that each aberration is corrected satisfactorily.

  Further, the total optical length TTL is as short as 4.69 mm, and the ratio (TTL / 2IH) to the maximum image height IH is 0.84. Further, the F value is as bright as 2.52, and the half angle of view is about 35.8 °, and a wide angle of view is realized.

Basic lens data is shown in Table 6 below.

  The imaging lens of Example 6 satisfies all conditional expressions (1) to (10) as shown in Table 7.

  FIG. 12 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 6. As shown in FIG. 12, it can be seen that each aberration is corrected satisfactorily.

  Further, the total optical length TTL is as short as 4.49 mm, and the ratio (TTL / 2IH) to the maximum image height IH is 0.80. Further, the F value is as bright as 2.53, and the wide angle of view is realized with a half angle of view of about 35.7 °.

  Although the imaging lens according to the embodiment of the present invention has a five-lens configuration, the optical total length TTL is 5 mm or less, and the ratio (TTL / 2IH) between the optical total length and the maximum image height IH is 0.85 or less. The miniaturization has been achieved. In addition, the aberrations are well corrected, the F value is about 2.5 and it is bright, and the entire angle of view is around 72 °, which enables photographing with a wide angle of view.

Table 7 shows values of conditional expressions (1) to (10) of Examples 1 to 6.

  The imaging lens having a five-lens configuration according to each embodiment of the present invention is an imaging optical system that is mounted on a mobile terminal such as a mobile phone or a smartphone, a PDA (Personal Digital Assistance), etc. It can be suitably applied to. According to the imaging lens of the present invention, the imaging optical system and the like can be improved in performance, size, and wide angle of view.

ST Aperture stop L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens IR filter

Claims (7)

An imaging lens composed of five lenses for a solid-state imaging device, in order from the object side to the image side, an aperture stop, a first lens having a positive refractive power with a convex surface facing the object side, and an image A second lens having a negative refractive power with the concave surface facing the side, a third lens having a positive refractive power with the convex surface facing the image side, and both surfaces are formed of an aspheric surface, and the concave surface on the object side in the vicinity of the optical axis A fourth lens having negative refractive power directed to the lens, and a fifth lens having negative meniscus power having both surfaces formed of aspheric surfaces and having a concave surface facing the image side in the vicinity of the optical axis, Is an imaging lens having a shape in which the negative refractive power is weakened with distance from the optical axis, and satisfies the following conditional expression (1).
(1) 0.55 <f1 / f <1.0
However,
f: focal length of the entire imaging lens f1: focal length of the first lens The imaging lens according to claim 1, wherein the following conditional expressions (2) to (6) are satisfied.
(2) 50 <ν1 <70
(3) ν2 <35
(4) 50 <ν3 <70
(5) 50 <ν4 <70
(6) 50 <ν5 <70
However,
ν1: Abbe number of the first lens ν2: Abbe number of the second lens ν3: Abbe number of the third lens ν4: Abbe number of the fourth lens ν5: Abbe number of the fifth lens The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied.
(7) -1.6 <f2 / f <-0.7
However,
f2: focal length of the second lens The imaging lens according to claim 1, wherein the following conditional expression (8) is satisfied.
(8) 1.05 <f12 / f <1.60
However,
f12: Composite focal length of the first lens and the second lens   The object-side surface of the fourth lens has an aspherical shape in which negative power is weakened toward the periphery, and the image-side surface has an aspherical shape in which positive power is weakened toward the periphery. The imaging lens according to claim 1. The imaging lens according to claim 2, wherein the following conditional expression (9) is satisfied.
(9) 1.7 <ν1 / ν2 <2.7
However,
ν1: Abbe number of the first lens ν2: Abbe number of the second lens The imaging lens according to claim 1, wherein the following conditional expression (10) is satisfied.
(10) −0.80 <f1 / f2 <−0.45
However,
f1: Focal length of the first lens f2: Focal length of the second lens

Images